DeskTop Dyno - Quick Tech Inspection

Education is expensive, especially if experience is your teacher. But what if we told you there was a way to learn about the effects of a camshaft, cylinder heads, compression, valve size, and intake and exhaust tuning on engine power for only $40? Would you do it? If you're smart you would.

This inexpensive teacher comes in the form of the latest engine-simulation computer program from Mr. Gasket called the DeskTop Dyno (part No. 3618). This software uses sophisticated programming combined with simple menus to allow you to "build" an engine and subject it to a simulated dyno test. The estimated power curve is then represented on a graph plotting torque and horsepower.

In order to keep the software affordable, the inputs are limited to seven basic parameters that affect engine power: displacement, head/port design and valve diameters, compression, carburetor size, intake manifold, exhaust, and camshaft specs. For example, rather than requiring flow bench numbers, the head/port design input estimates head flow based on several different categories, such as stock pocket-ported or fully ported heads. There's also a separate category for four-valve heads. However, camshaft input can be very accurately expressed in a number of different ways depending on how much information you have about the cam.

On the output side, the program will deliver not only the simulated power numbers on a chart, but it also graphs the entire horsepower and torque curves. The best part of this program is its ability to make quick changes to a combination and instantly judge the results. To evaluate this program's accuracy, we input data from previously tested 383ci and 420ci small-block Chevy engines into the program.

For the 383, the power estimates at 2000 and 2500 rpm were roughly 10 percent high. But above that, the DeskTop Dyno torque estimates exceeded the actual engine's power curve by an average of slightly more than 13 lbs-ft, including a 4000-rpm power estimate that was high by 30 lbs-ft. Looking at the data, that 30-lbs-ft "overshoot" is actually closer to what the engine should have made, since the real engine lost power at 4000 rpm due to a lean spot in the carburetor's fuel curve, while the program assumes an ideal air/fuel ratio. The power estimate on the 420ci engine was even more accurate, with an average difference of only 3 lbs-ft and the program's greatest "miss" of only 6 lbs-ft.

Despite the DeskTop Dyno's low $42.95 list price, this appears to be a highly accurate program. Each horsepower and torque datum point requires more than a million separate calculations, which means your PC should be at least a 386SX to reduce the amount of computer time for each test. DOS 3.1 or later is required, and while a mouse will speed up the selection process, it's not necessary.

As an inexpensive learning tool to evaluate engine component changes without the brutal cost of building and testing the engine, this program is perhaps the best investment any hot rodder could make. While no engine-simulation program is entirely accurate, for the money Mr. Gasket's DeskTop Dyno is hard to beat.